iChat's "Get an iChat account" no longer works in Mac OS X v10.6.x.
This feature has been replaced by iCloud, which requires OS X Lion v10.7.2 or later.
With OS X Lion, you can use an iCloud account ending in @me.com or @mac.com as your iChat account. A free AIM account can be acquired (or configured) separately at the AIM website.
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